1. Field of the Invention
This invention relates to cleaning compositions, specifically cosmetic compositions such as shampoos, bubble baths and other bath products. More specifically, it relates to compositions having good foaming properties and very low eye irritation. The invention finds particular utility in the preparation of shampoos having a low level of eye irritation.
2. Description of the Prior Art
Cosmetic cleaning compositions, particularly those used as shampoos, should produce stable foams of high volume. The amount and stability of the foam are directly related to the perceived cleaning efficiency of the composition. In addition, these compositions should produce little or no irritation to the eyes and skin.
Anionic surfactants, such as anionic sulfates, have excellent cleaning and foaming properties. As a result, many shampoos and other cosmetic cleaning compositions contain anionic sulfates. However, the anionic sulfates at concentrations used in these compositions irritate the skin and eyes. Therefore, they must be modified or combined with other reagents in order to reduce the irritation to a level which is commercially acceptable.
It is known that the irritation caused by anionic sulfates can be reduced by ethoxylation. However, this reduction in irritation is accompanied by a corresponding reduction in foam volume. Thus, sodium lauryl sulfate, a high foaming surfactant, causes significant eye irritation. In contrast, sodium laureth-12 sulfate (sodium lauryl ether (12) sulfate) is almost completely non-irritating, but is a poor foaming agent. (See Schoenberg, "Baby Shampoo," Household & Personal Products Industry 60 (September 1979).) The poor foaming properties of ethoxylated alkyl sulfates is reported in many other publications. For example, U.S. Pat. No. 4,132,678 discloses that the foaming properties of alkyl (C.sub.10 -C.sub.18) sulfates is drastically reduced if more than five ethoxy groups are added to the molecule.
Prior to this invention, shampoos having both low irritation and good foaming properties were made by combining a good foaming agent with an anti-irritant. One example of this type composition is found in Schoenberg where a blend of sodium laureth-12 sulfate and cocamidopropyl betaine is reported to have eye irritation and foaming properties "on a par" with an unidentified national brand of baby shampoo.
A composition containing a surfactant betaine and an alkyl ether sulfate is also disclosed in U.S. Pat. No. 3,950,417. This composition contains a long chain betaine-anionic surfactant complex in combination with a highly soluble non-anionic polyoxyethylene sorbitan ester. The preferred betaine-anionic surfactant complex is a combination of cocamidobetaine and tridecyl (4.4) ether sulfate. The preferred polyoxyethylene sorbitan ester is polyoxyethylene (44) sorbitan monolaurate. Although the patent is silent on the purpose of the polyoxyethylene sorbitan ester, its purpose presumably is to reduce the irritation caused by the betaine-anionic complex. (See Norda Briefs No. 479 (March 1977).) Polyoxyethylene (20) sorbitan monolaurate is the anti-irritant that is used in a commercial baby shampoo. (Id.)
Another composition containing alkyl ether sulfates which is allegedly nonirritating is disclosed in U.S. Pat. No. 4,110,263. Here an alkyleneoxylated bisquarternary ammonium compound is said to decrease the occular irritancy produced by anionic detergents and permit formulation of compositions to maximize cleaning properties. Among the anionic detergents disclosed are tridecyl ether (4) sulfate and tetradecyl ether (3) sulfate.